The adsorption of sulphur dioxide (SO2) on two bentonites from Unye, Turkey (Kavaktepe and Yemis litepe deposits – denoted below as BK and BY) and on forms treated with 1 and 2 m HCl solutions was investigated. The bentonite samples were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), thermogravimetry (TG-DTG), differential thermal analysis (DTA) and nitrogen adsorption methods. Adsorption capacities of SO2 were obtained using a standard volumetric apparatus at 293 K and 106 kPa. The SO2 adsorption capacity of the BY-2 (1.263 mmol g–1) sample was much greater than the BK-2 (1.126 mmol g–1) sample. As the concentration of acid increased, the specific surface areas and the uptakes of SO2 gas increased.